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No. 60: Nov-Dec 1988

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Purposeful evolution?

One seemingly unassailable dogma of evolutionary biology insists that natural selection involves, first, the continuous, random, environment-independent generation of genetic mutations; and, second, the subsequent fixation of those mutations that are favored by prevailing conditions. In other works, the genetic mutations cannot be influenced by external events and conditions. But in recent experiments with bacteria (E. coli), J. Cairns et al, at the Harvard School of Public Health, find they actually do produce mutations in direct response to changes in their environment. The adjective "purposeful" has even been applied to the action of these bacteria! Can anything be more heretical?

"One of the experiments involves taking colonies of E. coli that are incapable of metabolizing lactose and exposing them to the sugar. If the lactose-utilizing mutants simply arise spontaneously in the population and are then favored by prevailing conditions, then this would lead to one pattern of new colony growth. A distinctly different pattern is produced if, under the new conditions, the rate of production of lactose-utilizing mutants is enhanced. The observation is something of a mixture of patterns, indicating that directed mutation appears to be occurring. 'This experiment suggests that populations of bacteria...have some way of producing (or selectively retaining) only the most appropriate mutations,' note Cairns and his colleagues."

(Lewin, Roger; "A Heresy in Evolutionary Biology," Science, 241:1431, 1988.)

Research with E. coli at other labs is producing similar heresy. Cairns does not doubt that some mutations arise spontaneously and randomly, but some bacteria have found a way to do a little better.

(Hendricks, M.; "Experiments Challenge Genetic Theory," Science News, 134:166, 1988. Also: Cherfas, Jeremy; "Bacteria Take the Chance out of Evolution," New Scientist, p. 34, September 22, 1988.)

Comment. This discovery seems at least as "impossible" as the "infinite dilution" experiments discussed elsewhere. Will Nature now dispatch a "hit squad" to Harvard?

From Science Frontiers #60, NOV-DEC 1988. 1988-2000 William R. Corliss